The objective of this research is the study of the functions involved in progression through the G1 and S phases of the cell cycle in somatic animal cells and the study of the functions regulating gene transfer and gene rearrangements in animal cells. Our work is planned along three main lines of research: (1)\the study of gene transfer in animal cells with particular regard to the state of the transferred gene(s), its modality of integration and its expression; (2)\the study of the program of transcription of specific genes in the cell cycle and the effect of defined cell cycle mutations on the development of this program; (3)\the study of the effects of polyoma virus proteins on the rearrangements (particularly amplification) of cellular genes in transformed cells.